Strong coupling between a dielectric nanocavity and a monolayer transition metal dichalcogenide

We demonstrate strong coupling between light in a dielectric nanocavity with deep subwavelength confinement and excitons in a monolayer of molybdenum ditelluride. Avoided crossing is demonstrated by both photoluminescence and reflection measurements, from which we extract a light-matter interaction strength of g PL = 5.3 ± 0.3 m eV and g R = 4.7 ± 0.7 m eV , respectively. The associated Rabi splitting is twice as large as the system's losses. These values are in good agreement with values obtained by an exciton reaction coordinate formalism, yielding g theory = 5.2 ± 0.7 m eV . The strong light-matter interaction, combined with low losses and subwavelength confinement of light, demonstrates a regime of light-matter interactions where strong nonlinearities at the single-photon level are expected.